The right kind of motor is needed when designing a unit that needs to deliver motion. Unlike a regular motor, a servo motor is capable of producing precise control of acceleration, velocity, and angular position. Servo motors are composed of an electric motor, a feedback device, and some kind of electronic control system. The electric motor either runs on AC or DC power. The DC has two classifications: brushed and brushless servo motors.
What Is a Servo Drive?
Automatic devices, servomechanisms, or servo systems have four components: a drive, a motor, a controller, and a feedback device. The controller sets what the servo drive motor must produce. It then triggers the drive to send the required electrical energy to the motor. As a result, the desired motion takes place.
Basically, servo drives act as an electronic amplifier. It transmits the amount of voltage and current needed for the motor to perform the required motion. A servo drive can provide automatic systems with superpositioning, speed, and motion control.
Brushless Servo Motors
From the name itself, this servo motor doesn’t use brushes. How do they work? Brushless servo motors have two or more permanent magnets installed to the rotor which rotates in a fixed stator in an external-rotor configuration. To control the ongoing supply to the stator, a special solid-state circuit is applied. The rotation speed, as well as, the angle of the rotor is defined by this electronic sensor. It makes sure that electromagnets produce torque flowing in one direction. Because brushless servo motors have permanent magnets, their rotors and stators turn at the same frequency, making them synchronous.
Benefits of Brushless Servo Motors
There are different applications for brushless servo motors. For one, automated machinery primarily uses digital servo drive for brushless motors to achieve accurate positioning of the work tool or workpiece. Other examples of high-quality brushless servo drive applications include robotics, semiconductor fabrication, and machine tool axes. Some of the benefits of using a brushless servo motor are:
- Long life expectancy
- High-efficiency indicators
- Minimal noise level
- Quickly achieves maximum rotation speed
- Fewer maintenance requirements
- Doesn’t require additional cooling resources
Disadvantages of Brushless Servo Motors
Although brushless servo motors are generally used in many applications, they still have some disadvantages.
- More expensive because of high-priced components
- A restricted number of resources for electrical elements
- Requires more commutating devices to work, such as encoders, drives, and commutators
- Complicated management system
On the other hand, brushed servo motors have a stator with two magnets that enclose a turning rotor or armature. Reversed polarities generate a magnetic field torque when connected to a current source. This makes the rotor begin revolving around its axis.
Between the rotor and the stationary part of the machine is where the electric current moves. The flow of the electric current is switched with a commutator. The commutator has two components: the collector and brushes. The collector is a set of contacts positioned in the rotor. Meanwhile, the brushes are placed on the exterior part of the rotor and pressed to the collector.
Benefits of Brushed Servo Motors
Because brushed servo motors can work without onboard electronics, they are generally used in various applications with extreme environmental conditions. Brushed servo motors are also used in small appliances, consumer goods, battery-powered devices, automotive, and other applications. Here are the reasons why it’s good to use a brushed servo motor:
- Easy to maintain
- Less expensive
- Higher resistance
- Simple wiring and design
- Can withstand mechanical and vibration shocks
Disadvantages of Brushed Servo Motors
One must first acquire enough information before using brushed servo motors. One wrong move will result in consequences. For example, exceeding the density may burn the brushes. Also, extra speed can fly off the commutator. Take note of some disadvantages of the brushed servo motor:
- Bigger and heavier commutator and brushes
- Brushes may get damaged quickly
- Steady mechanical noises
- Low efficiency
- Reduced service life
Both brushed and brushless servo motors add great features to a lot of automated systems we use. However, the clear winner between the two is the brushless motor. Why? Because they are proven to be more effective in converting electrical energy into mechanical energy. Furthermore, they last longer than brushed motors. Yes, brushed motors may have lesser power and stability, but they can still be used for moderate-to-low speed applications.
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